Modern elevator concepts for buildings with thirty and more floors have transfer floors which are served by an elevator installation. Such an elevator installation comprises a group of at least two elevators. A first elevator directly serves the transfer floors from an entrance lobby, i.e. passengers are coarsely distributed relatively quickly from the entrance lobby by a high-speed elevator to the different transfer floors. A second elevator carries out fine distribution of the passengers from the transfer floors to the destination floors thereof.
An elevator usually comprises an elevator car, which is vertically movable in a shaft and receives passengers in order to transport these to a desired floor of a building. In order to be able to look after this task the elevator usually has at least the following elevator components: a drive with a motor and a drive pulley, deflecting rollers, tension means, a counterweight as well as a respective pair of guide rails for guidance of an elevator car and the counterweight.
In that case the motor produces the power required for transport of the passengers present in the elevator car. An electric motor usually looks after this function. This directly or indirectly drives a drive pulley, which is in friction contact with a tension means. The tension means can be a belt or a cable. It serves for suspension as well as conveying the elevator car and the counterweight, which both are so suspended that the gravitational forces thereof act in opposite direction along the tension means. The resultant gravitational force which has to be overcome by the drive, correspondingly substantially reduces. In addition, due to the greater contact force of the tension means with the drive pulley a greater drive moment can be transmitted by the drive pulley to the tension means. The tension means is guided by deflecting rollers.
The optimum utilization of the shaft volume has ever increasing significance in elevator construction. Particularly in high-rise buildings with a high degree of utilization of the building a management of the passenger traffic as efficiently as possible for a given shaft volume is desired. This objective can be achieved firstly by an optimum space-saving arrangement of the elevator components, which creates space for larger elevator cars, and secondly by elevator concepts which enable vertical movement of several independent elevator cars in one shaft.
European patent document EP 1 526 103 shows an elevator installation with at least two elevators in a building, which is divided up into zones. A zone in that case comprises a defined number of floors which are served by an elevator. A zone is allocated to each elevator. A transfer floor is provided in order to go from one zone to another zone. At least one of the elevators has two elevator cars which are movable independently of one another vertically one above the other at two car guide rails. The arrangement of two fetch or carry cars is to assist with preventing unnecessary waiting times at the transfer floors.
An elevator with at least two elevator cars disposed one above the other in the same shaft is shown in European patent document EP 1 489 033. Each elevator car has an associated drive and an associated counterweight. The drives are arranged near first and second shaft walls and the counterweights are also respectively suspended below the associated drive at drive or holding cables near first or second shaft walls. The axes of the drive pulleys of the drives are disposed perpendicularly to the first and second shaft walls. The two independently movable elevator cars ensure a high conveying performance. The positioning of the drives in the shaft near first or second walls renders a separate engine room superfluous and enables a space-saving, compact arrangement of the drive elements in the shaft head.